On Fri, 28 Jun 2024 at 07:53, Maciej Cencora wrote:
>
> But constexpr-ness of bit_cast has additional limitations and e.g. providing
> an union as _Tp would be a hard-error. So we have two options:
> - before bitcasting check if type can be bitcast-ed at compile-time,
> - change the 'if constex
But constexpr-ness of bit_cast has additional limitations and e.g.
providing an union as _Tp would be a hard-error. So we have two options:
- before bitcasting check if type can be bitcast-ed at compile-time,
- change the 'if constexpr' to regular 'if'.
If we go with the second solution then we
On Thu, 27 Jun 2024 at 14:27, Maciej Cencora wrote:
>
> I think going the bit_cast way would be the best because it enables the
> optimization for many more classes including common wrappers like optional,
> variant, pair, tuple and std::array.
This isn't tested but seems to work on simple case
I think going the bit_cast way would be the best because it enables the
optimization for many more classes including common wrappers like optional,
variant, pair, tuple and std::array.
Regards,
Maciej Cencora
czw., 27 cze 2024 o 14:57 Maciej Cencora napisał(a):
> You could include some of the b
You could include some of the bigger classes by checking whether the class
type is bit_cast-able to std::array of bytes, and that bitcasted output is
equal to value-initialized array.
Regards,
Maciej
czw., 27 cze 2024 o 14:50 Jonathan Wakely napisał(a):
> On Thu, 27 Jun 2024 at 13:49, Jonathan
On Thu, 27 Jun 2024 at 13:49, Jonathan Wakely wrote:
>
> On Thu, 27 Jun 2024 at 13:40, Maciej Cencora wrote:
> >
> > Hi,
> >
> > not sure whether I've missed some conditional that would exclude this case,
> > but your change seems to incorrectly handle trivial types that have a
> > non-zero bit
On Thu, 27 Jun 2024 at 13:40, Maciej Cencora wrote:
>
> Hi,
>
> not sure whether I've missed some conditional that would exclude this case,
> but your change seems to incorrectly handle trivial types that have a
> non-zero bit pattern of value-initialized object, e.g. pointer to member.
Good poi
Hi,
not sure whether I've missed some conditional that would exclude this case,
but your change seems to incorrectly handle trivial types that have a
non-zero bit pattern of value-initialized object, e.g. pointer to member.
Regards,
Maciej Cencora
On Thu, 27 Jun 2024 at 11:53, Jonathan Wakely wrote:
>
> For trivial types std::__uninitialized_default (which is used by
> std::uninitialized_value_construct) value-initializes the first element
> then copies that to the rest of the range using std::fill.
>
> Tamar is working on improved vectoriz
For trivial types std::__uninitialized_default (which is used by
std::uninitialized_value_construct) value-initializes the first element
then copies that to the rest of the range using std::fill.
Tamar is working on improved vectorization for std::fill, but for this
value-initialized case where we
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